По какой причине человек может смеяться?

Animals never laugh, but a person was able to assess the comic situation and use this assessment for his own purposes, the main of which is not just entertainment of oneself, but a distraction from the troubles and hardships of life, which a person is aware of, but cannot do anything. Therefore, it is not so easy to understand the essence of the comic, but you can try.

Extremely effective way of distracting a person from the troubles and hardships of life is partly the transformation of them into the comic. By such detachment from reality in laughter, a person is freed from the conventions of being, instinctively sensing their temporality and imperfection.
The external expression of this curious transformation tribulations, and tragedies into the comic, detract from them, is the laughter, the animal component of which comes from the reflexes, similar of a reaction to scratching, and the essential component is determined by the consciousness in the form of a relationship to some troubles and misfortunes as to the absurdity of the unexpected incident with yourself or preferably with others.
Absurdity of it, dropping out of a framework of the known order, causes involuntary fun or an ironical grin from that, as "to those above" cannot provide the order in "hostel".